1. Field of the Invention
The present invention is generally related to nuclear reactors and particularly to nuclear propulsion reactors.
2. General Background
Desirable features of nuclear propulsion reactors for vehicles to be used in outer space are a high thrust-to-weight ratio and high exhaust temperature. Unfortunately, these are conflicting requirements where nuclear reactors are concerned. A high thrust-to-weight ratio tends to require low density materials while a high exhaust temperature tends to require high density materials. When these two features are sought in a single reactor core, the result is invariably a compromise in the core design that leads to a lower thrust-to-weight ratio and/or exhaust temperature than might otherwise be possible. In previous space nuclear propulsion reactor concepts the propellant gas is heated from its cryogenic inlet temperature to its final exhaust temperature by a single core region. This is the case for the ROVER/NERVA type engines that have been built and tested and known conceptual designs. This leaves a need for a nuclear propulsion reactor that provides a thrust-to-weight ratio and exhaust temperature that is more favorable than that of current designs.